Harder clutch pedal after new OEM clutch installed and not as responsive

The Subaru dealership I took my '07 WRX to said that my clutch pedal was stiff and that I needed a new clutch. Ok, so I got the clutch replaced with an OEM one and they resurfaced the flywheel. When I initially got it back, I tried to drive it around the block and for some reason the brake was being applied at all times and it was incredibly slow. I immediately took it back and they said it had something to do with an adjustment at the pedals. So anyway, they fixed that but I noticed that the car did not have the same "forward thrust" that it used to when it hit 3K RPM. Now, when the car is cold it has the old feel to the clutch pedal (easier to press down) and the car has that zip to it. But most of the time the pedal is pretty stiff and it doesn't have the acceleration that it used to. Unfortunately I just moved away before I could get them to look at it again. Any ideas? Maybe air in the line of the slave cylinder?